It is well known to protect an information storage disk from dust and other contamination by enclosing it in a protective, rigid or semi-rigid cartridge shell which is provided with a movable shutter biased to normally close a disk access opening formed in the shell. A shutter opening mechanism is generally provided in the disk drive system to open the shutter automatically as the cartridge is inserted so as to allow access of a read/write head to the disk.
In general, such opening mechanisms may include one or more members positioned inside the drive which contact the shutter as the cartridge is inserted longitudinally into the drive and force the shutter to move laterally to expose the disk access opening. In the case of flexible magnetic disk cartridges, the magnetic read/write heads are typically held pivoted away from the plane of the disk until the cartridge is fully inserted with the shutter open and the disk exposed whereupon the heads are brought into contact with the disk. Since magnetic read/write heads are relatively small and the width of the radial band traversed by the scanning heads is generally relatively narrow, the cartridge access opening can be correspondingly narrow and the disk can be adequately exposed with relatively short lateral movement of the shutter.
With the advent of optical and magneto-optical information storage technology, read/write heads have become more bulky in order to accommodate the optical components required to generate the laser beam which is focused onto the disk surface for read and/or write functions. Moreover, for good signal-to-noise performance, the head with its beam objective lens must be maintained quite close to the surface of the disk, usually within 1-2 millimeters, as the head scans across the information storage tracks. This requires that the disk access opening in the cartridge be larger than is used for magnetic disk cartridges. Additionally, in the case of magneto-optical systems, a relatively large access opening in the cartridge also must be provided to allow an electromagnetic bias coil to be maintained in similar close proximity to the disk surface on which the magneto-optical media resides for effective operation during the write function. In addition to providing for access by the head objective lens and bias coil, it is also necessary in some cases to provide for access by a disk clamp mechanism used to clamp a central hub region of the disk to a spindle-drive. Such a clamp is typically located on the opposite side of the disk from the spindle-drive.
It is typically very important to minimize the volume taken up by the cartridge loading and unloading mechanism in disk drive systems, particularly for mini and microcomputer applications. An effective way to accomplish this objective is to maintain the cartridge and its enclosed disk in an operating position within the drive system that is in the same plane as the cartridge insertion plane with the drive-spindle, disk clamp and bias coil being brought into operating position with the disk after the cartridge is in its fully inserted position.
In order to maintain the optical read/write head and the bias coil and disk clamp in proper spaced relationship from the surface of the disk with a minimum of costly mechanical design complexity, it is highly desirable that these elements remain fixed in the axial direction relative to the disk surfaces and thus become nested within the disk access opening as the cartridge is inserted longitudinally into the disk drive system. This requires not only that the disk access opening be wide enough from the leading edge to as far as the central hub to accommodate these elements, but also that the shutter be fully opened before these elements are encountered during insertion. A further consideration is the desire to have the shutter maintained in the closed position covering the disk access opening until the cartridge has been inserted far enough into the drive system that at least the track area, and preferably also the central hub region of the disk, be protected by the drive system from accidental contact by the user when the shutter begins to open. As a consequence, the shutter must opened very quickly over a very short span of cartridge insertion travel in order to clear the read/write and disk clamp elements while at the same time protecting the disk surfaces from accidental contact by the user during insertion.
It is therefore an object of the present invention to provide a shutter opening mechanism for an information storage disk drive system that is low in cost and is capable of rapidly opening the shutter over a short span of cartridge insertion travel.